squee, returns all data as strings, and expects strings as inputs to
queries. So, keeping the ids as strings was easy initially, but it means that
you can't tell from the type whether it should be quoted, or not...
Therefore, handle ids as strings, converting them to numbers when they're
fetched from the database, and back to strings as part of the queries.
Rather than just storing the URL in the guix_revisions and
load_new_guix_revision_jobs tables. This will help when storing more
information like tags and branches in the future.
